As per people, letters are different. You find some people are quiet, other are loud. But regardless of this, there are places when even the loud ones must be quiet! Take for example, the library or art gallery.

In Tajweed there are rules regarding the silent noon[1]. This is known as âAl-Noon Al-Saakinahâ in Arabic. The rules regarding the silent noon also apply to tanween [2].
Rule One: Ith-haar Al-Bayan (where the noon/tanween is pronounced clearly).
Itâs pronounced clearly only when the following is true:
The noon has a sukoon[3] on it (ÙÙ) and one of the following letters come after it (whether in the same word or following one)[4]:
alif, haa, khaa, ayn, ghayn, haa
ÙÙ Â Â Â Űș     Űč    ۟     Ű    ۣ
Note this also applies for the Tanween.
Examples of this are as follow:
example one: hakeemin hameedâŰÙÙÙ Ù ŰÙ ÙŰŻ
example two: an aqeemoo â ۣÙÙ ŰŁÙÙÙ Ùۧ
Please note that I have put up very beneficial documents under the âresourcesâ page. I hope these are of benefit.
Resources Link:
â Tanween [Gateway to Arabic: page 40]
[Tajweed Basics: Foundations and More: pages 11 â 14]
â Sukoon [Gateway to Arabic: page 48]
[1] â noon: the 25th Arabic letter, that makes a ânâ sound, such as in the words, ânâear, ânâor, Aânnâ. The letter in arabic is written as Ù
An interesting website all about the letter noon is here: http://www.meem.freeuk.com/Noon.html
[2] â The tanween is an ânâ sound added to the end of the word in certain circumstances, usually it functions just like the âaâ and âanâ in English, indicating an indefinite article. The word tanween, usually translated as ânunationâ, means âto ân’â, or âânâingâ, making an ânâ sound. There are three types of tanween:
1-Â fat-ha tanween
2 â kasra tanween
3 â damma tanween
fat-ha tanween: The fat-ha tanween is pronounced âanâ, as in âanimalâ.
kasra tanween: The kasra tanween is pronouced âinâ, as in âinâ, âtinâ, âfinâ, etc. Some native Arabic speakers might indicate a kasra tanween with an âenâ, thinking that âeâ sounds like the Arabic âyaaâ letter. This is a mistake that stems from not knowing how native English speakers pronounce the âeâ sound.
damma tanween: The dhamma tanween is pronounced as a short âooâ followed by an ânâ. This sounds like the short âunâ in âunoâ, not like the long âoonâ in âsoonâ.
tanween at the end of a sentence: If the tanween is the last thing in the sentence, itâs not pronounced. In the case of a fat-ha tanween, the alif is pronounced as a long vowel.
[3] â More about sukoon can be found here: http://en.wikipedia.org/wiki/Arabic_diacritics#Suk.C5.ABn
[4]Â â More about these letters can be found here:Â http://www.meem.freeuk.com/Â scroll down to the âABJAD TABLEâ and select one of the abovementioned letters to learn more about it.